Hybrid Fluid-Flow Fitting Assembly

ABSTRACT

A hybrid fluid-flow assembly having a base fitting that has been formed by axial load bulge forming from a sheet of metal, and a custom fitting that has been machined from a shaped-memory alloy. The input port of the custom fitting is connected to the output port of the base fitting by an interference fit. The interference fit may be formed by cooling the custom fitting to a temperature below its transition temperature, deforming the custom fitting so that the diameter of an inlet port is slightly larger than an output port on the base fitting, installing the input port of the custom fitting on the output port of the base fitting, and allowing the custom fitting to warm to room temperature. The shaped-memory alloy swages and coins the outer surface of the base fitting at the interface of the ports, thereby forming a compressive, interference fit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional patent application claims priority to U.S.provisional patent application No. 62/521,478, filed Jun. 18, 2018entitled Hybrid Fluid-Flow Fitting Assembly, which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to a hybrid assembly of fluid-flowfittings that comprise different materials and/or have been made usingdifferent manufacturing methods, which are connected in a unique manner.

BACKGROUND OF THE INVENTION

A fitting is used in fluid-flow systems to connect tubing sections,adapt to different sizes or shapes and for other purposes, such asregulating (or measuring) fluid flow. Some common fluid-flow fittingsinclude elbows, couplings, unions, reducers, tees, crosses and caps. Inaddition to domestic and commercial plumbing, fittings for carrying oil,air, water and fuel are commonly used in many industries, includingaircraft and other turbine-based engines.

In prior art applications where weight is not an issue, fluid-flowfittings are often machined from forgings of various material. Fittingsmachined from forgings are typically heavy because much of the forgedmaterial remains after machining. While the added weight reduction fromadditional machining may justify the added cost in the aircraft andaerospace industries, it would be desirable to provide a method ofmaking a lightweight fitting for universal use that is more efficientthan machining from forgings.

Fittings machined from cast forgings have other shortcomings. Forexample, the internal flow path of such fittings is not smooth, whichcan create a turbulent or interrupted flow path. Also, such fittingsonly often have one attachment style/structure (e.g. threading) due tothe fact that the fitting is machined from the specific forging.Therefore, it would be desirable to provide a fitting assembly having asmooth flow path and a variety of attachment styles/structures.

Axial-load bulge forming (“ALBF”) is a known technique for manufacturingcomplex products, such as aircraft, jet engine, and other aerospacecomponents, which cannot be produced cost effectively by conventionalmethods such as hydroforming, stamping, drop hammer forming, orspinning. ALBF can be used to produce complex shapes from thin-walledsheet with minimal material thin-out. While ALBF may be useful formaking some fittings, such as reducers, tees, crosses, or wyes, ALBFcannot be used to make some other necessary fittings such as threadednipples or unions, which require much heavier wall thicknesses.Therefore, it would be desirable to provide a method of making a fittingassembly having both lightweight, thin-walled components andthick-walled components.

Common, ALBF fittings such as reducers, tees, crosses, or wyes, areoften combined with a variety of other fittings. It is costly to produceand stock a large number of common ALBF fittings having a variety ofdifferent types and sizes of connectors integrally formed or connectedthereto. Rather than stocking such a large number and variety of commonALBF fittings, it has been proposed to stock a limited number of“standard” ALBF, thin-walled fittings, which can be connected by acustomer by welding or swaging to more “customized” fittings/connectors.However, connecting ALBF and customized fittings can be difficult forseveral reasons. The legs of thin-walled, ALBF fittings can have anon-uniform wall thickness, which makes them difficult to weld. The legsof these base fittings are often short, which makes them difficult toconnect to prior art swage fittings. The legs of these base fittings areoften out-of-round, which makes it difficult to obtain a leak-freeconnection. ALBF and customized fittings are often made from differentmaterials, which also makes them difficult to weld. Therefore, it wouldbe desirable to provide a method of easily and reliably connecting acustomized fitting to a standard, thin-walled fitting made by ALBF.

SUMMARY OF THE INVENTION

The present invention provides a hybrid assembly of fluid-flow fittingsthat comprise different materials and/or have been made using differentmanufacturing methods. The individual fittings are connected in a uniquemanner that overcomes some difficulties in the prior art. In onepreferred embodiment, the assembly comprises the combination of astandard or base ALBF fitting and an SMA fitting, which can be used toconnect another fluid-flow element such as tubing to the ALBF fitting.In another preferred embodiment, the assembly comprises the combinationof a standard or base ALBF fitting and an SMA fitting, which can be usedto connect another standard fitting to the ALBF fitting. A variety ofALBF and SMA fittings can be provided in a kit so that the user cancombine the fittings in a plurality of hybrid assemblies, which arecustomized for a particular application.

In one preferred embodiment, the hybrid fluid-flow assembly generallycomprises base, fluid-flow fitting connected to a custom fluid-flowfitting. The base fitting preferably has been formed by axial load bulgeforming from a sheet or tube of thin metal. The base fitting has aninput port, at least one output port, and a fluid-flow channelconnecting said input and output ports. The custom fitting haspreferably been machined from a cast, shaped-memory alloy. The customfitting has a parent shape, a martensitic shape, an output port, aninput port having an inner diameter in its martensitic shape slightlylarger than the outer diameter of the output port of the base fitting,and a fluid-flow channel connecting the input and output ports. Theinput port of the custom fitting is connected to the output port of thebase fitting by an interference fit, preferably in its parent condition.

The novel connection method accommodates the condition wherein at leastone output port of the base fitting was out-of-round prior to formingthe interference fit. The novel connection method also accommodatesother adverse connection conditions of the prior art such as where thebase fitting and custom fitting are made from materials that are notweldable together, where traditional swage fittings cannot be used, orwhere the wall thickness is too thin to weld.

In another preferred embodiment, a fluid-flow assembly kit comprises abase fluid-flow fitting and a plurality of custom fluid-flow fittings aspreviously described. The input port of the custom fitting is connectedto the output port of the base fitting by an interference fit. Theplurality of custom fittings may have different output ports so that theuser can customize the assembly for a particular application. Theplurality of custom fittings have been cooled to and deformed at atemperature below their transition temperature. To prevent the customfittings from returning to their parent shape, the kit includes meansfor storing the custom fittings below their transition temperature.

In a further preferred embodiment, a method of making a custom fluidflow assembly comprises the steps of forming a base fluid flow fittingfrom a sheet of metal, machining a custom fluid-flow fitting from a castshaped-memory alloy, and creating a mechanical connection between thebase fitting and the custom fitting by installing the input port of thecustom fitting over an output port of the base fitting. The fittings areconstructed as described above. Preferably, the mechanical connection iscreated by deforming the custom fitting at a temperature below itstransition temperature, installing the custom fitting on the output portof the base fitting, and heating the custom fitting to form aninterference fit between the ports. In one preferred method, themechanical connection is created by deforming the custom fitting at atemperature far below room temperature and below its transitiontemperature, installing the custom fitting on the output port of thebase fitting, and allowing the custom fitting to warm to roomtemperature.

The use of an SMA fitting eliminates the need for welding or crimping.The compressive force of the SMA fitting returning to its parent shapeswages and/or coins the outer surface of the base fitting. Thecompressive force can compress an out-of-round port on the base fittingback to round, and can compress any surface defects, to ensure that aleak free seal is formed between the custom fitting and base fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art fitting manufactured bymachining a forged workpiece;

FIG. 2 is a perspective view of disconnected components of a preferredembodiment of the fitting assembly of the invention;

FIG. 3 is a perspective view of the components of FIG. 2 connected toform an assembly in accordance with a preferred embodiment of theinvention;

FIG. 4 is a perspective view of an assembly in accordance with anotherpreferred embodiment of the invention; and,

FIG. 5 is a perspective view of an assembly in accordance with yet afurther preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For the purpose of illustrating the invention, several embodiments ofthe invention are shown in the accompanying drawings. However, it shouldbe understood by those of ordinary skill in the art that the inventionis not limited to the precise arrangements and instrumentalities showntherein and described below. Throughout the specification, likereference numerals are used to designate like elements. Numerous changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

Unless otherwise defined, all technical and scientific terms used hereinin their various grammatical forms have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. As used herein, the term “shape-memory alloy” (“SMA”), alsoknown as smart metal, memory metal, memory alloy, muscle wire, and smartalloy, is an alloy that returns to its original (“parent”), pre-deformedshape after the temperature of the deformed shape is raised above itstransition temperature. As used herein, the term “transitiontemperature” means the temperature range over which an SMA transitionsfully from the austenitic phase to martensitic phase, and the reversetransformation.

A hybrid fluid-flow fitting assembly in accordance with a firstpreferred embodiment is illustrated in FIGS. 2-3 and is designated byreference numeral 10. The assembly 10 generally comprises a base fitting12 and a custom fitting 30 that are connected at overlapping fluid-flowports. In one preferred embodiment, the base fitting 12 is tee shapedand has a central body portion 12 a, an input leg 12 b, and two outputlegs 12 c, 12 d. An input port 14 is formed at the end of the input leg12 b. Opposed output ports 16, 18 are formed at the end of the outputlegs 12 c, 12 d, respectively. The base portion 12 a and legs 12 b, 12c, 12 d form fluid-flow channels connecting the ports.

In this embodiment, the base fitting is depicted as a tee. However, itshould be appreciated to those skilled in the art that the base fittingcould have a variety of other shapes without departing from the scope ofthe invention. For example, in other embodiments, the base fitting couldbe a cross, a wye, or a straight, smooth bore reducer or expander.

In a preferred embodiment, the base fitting 12 is formed from a thinsheet of metal or thin-walled tubing to reduce the weight of theassembly 10, which is especially important for aircraft and aerospaceapplications. The preferred material for base fitting will depend on itsapplication; however, some preferred materials include austeniticstainless steels, such as 321 and 347 grades, various titaniums(commercially pure, 3AI-2.5V), nickel alloys, such as 625 and 718grades, 3003 and 6061-0 aluminums. The base fitting 12 may be formedfrom known techniques; however, in the preferred embodiment shown inFIGS. 2-3, the base fitting 12 is made by axial load bulge forming(“ALBF”) from a sheet of metal or tubing. By using ALBF, the basefitting can have a wide variety of complex shapes.

In one preferred embodiment, the custom fitting 30 comprises a threadednipple having a generally-cylindrical, threaded body portion 30 a and aninput collar 30 b. An output port 32 is formed at the end of the outputcollar 30 b and is defined by the inner and outer walls of the collar.An input port 34 is formed at the opposed end of the body portion 30 a.The inner and outer diameters of the port are defined by the inner andouter walls of the input collar 30 b. The ports 32, 34 are connected byan internal fluid-flow channel extending through the body portion 30 aand collar 30 b. As described below, the inner diameter of the outputport 32 in the parent shape is slightly smaller than the outer diameterof the input ports 14 of the base fitting.

In a preferred embodiment, the custom fitting 30 is made from ashaped-memory alloy (“SMA”) such as Nitonol or Tinel (titanium nickelalloy), which has a transition temperature of about minus 150° F. Thecustom fitting 30 has a parent shape and a martensitic shape. The parentshape is the shape of the fitting 30 at room temperature after the castworkpiece has been machined to its final dimensions and finish. In theparent shape, the microstructure of the fitting 30 is entirelyaustenitic. The martensitic shape is the shape of the fitting 30 afterthe fitting 30 has been cooled to a temperature below the transitiontemperature and deformed to increase the diameter of the internal fluidflow channel or the output port 32. In the martensitic shape, themicrostructure of the fitting 30 is entirely martensitic.

The custom fitting 30 may be formed from known techniques. In apreferred embodiment shown in FIGS. 2-3, the base fitting 30 is made bymachining from a cast workpiece since SMA's are typically made bycasting. However, the custom fitting 30 could be machined from an SMAmade by other techniques. In other embodiments, the custom fitting couldbe made from other techniques such as casting.

In this embodiment, the custom fitting 30 is depicted as a nipple.However, it should be appreciated to those skilled in the art that thecustom fitting could have a variety of other shapes without departingfrom the scope of the invention. For example, in other embodiments, thecustom fitting could be a cap, union, barb, valve, etc. As describedbelow, in a further preferred embodiment, the invention comprises a kitincluding a variety of custom fittings that can be connected to astandard base fitting for creating a variety of customized fittingassemblies.

Referring to FIG. 3, the base fitting 12 and custom fitting 30 areconnected to form a hybrid fluid-flow fitting assembly 10. The fittingsare connected generally by an interference fit between the input port 14of the base fitting 12 and the output port 32 of the custom fitting 30.As discussed above, the inner diameter of the output port 32 in theparent shape is slightly smaller than the outer diameter of the inputport 14 of the base fitting. In a preferred embodiment, the interferencefit is created by first cooling the custom fitting 30 to a temperaturebelow its transition temperature. Then, the inner diameter of the entirecustom fitting 30 is expanded by known techniques, such as by using atapered mandrel, so that its inner diameter is slightly larger than theouter diameter of the input port 14 of the base fitting 12. In analternative embodiment, only the inner diameter of the output port 32 isdeformed and enlarged. Next, the output port 32 is installed over theinput port 14. Finally, the custom fitting 30 is allowed to warm to roomtemperature and return to its parent shape in which the inner diameterof the output port 32 is smaller than the outer diameter of the inputport 14 of the base fitting. The negative size differential between theoverlapping ports creates a compressive, interference fit at the portinterface.

In the embodiment shown in FIGS. 2-3, the custom fitting 30 is connectedto the input port of the base fitting. However, on or ordinary skill inthe art should appreciate that it could also be connected to one of theoutput ports. Therefore, the properties and design considerationsdiscussed below relate to any of the ports 14, 16, 18 or legs 12 b, 12 cor 12 d of the base fitting.

The dimensions and material of the custom fitting are preferablydesigned to provide sufficient compressive force by the custom fitting30 on the port to swage and seal against it and form a leak-proof seal.If the legs and/or ports of the base fitting are out of round whenoriginally formed, the compressive force of the custom fitting ispreferably high enough to deform the ports back to round. Because thereis a limit to the amount of total tolerance the custom fitting canaccommodate (percentage out of round+diameter tolerance), diameterexpansion of the custom fitting in the martensitic phase shouldpreferably be limited to about 8 percent to ensure complete recovery tothe parent shape.

The dimensions of the ports of the base fitting, particularly the wallthickness, are preferably designed to provide sufficient “resistance” tothe compressive force of the custom fitting 30. Preferably, the basefitting 12 should resist compression enough to allow some coining of itsouter surface, which eliminates small defects in the outer surface thatmay create leak paths. The dimensions of the ports will vary dependingon, among other things, the base fitting material and the operatingconditions of the assembly, discussed below, but should be readilydiscernable to one of ordinary skill in the art.

In addition to providing a good seal, the interference fit and coiningalso provide good resistance to axial loading. For high pressureapplications, such as an operating pressure up to 15,000 psi and a burstpressure of about 45,000 psi, the base fitting 12 should be formed fromthick-walled tubing made from a hard material such as, for example, 625Inconel. However, in such a case, the compressive force of the customfitting 12 will not deform the base fitting very much and may notprovide sufficient resistance to axial loading. To increase deformationand coining of the base fitting 12, the custom fitting 30 may be linedwith a harder material such as, for example, 718 Inconel, which providesa harder contact surface than the SMA material.

A hybrid fluid-flow fitting assembly in accordance with anotherpreferred embodiment is illustrated in FIG. 4 and is designated byreference numeral 110. The assembly 110 generally comprises a basefitting 112 and a plurality of custom fittings 130, 140, which areconnected at one end to the output legs 112 c, 112 d, respectively, ofthe base fitting 112, and at the other end to lengths of tubing 160. Thebase fitting 112 is identical in structure and manufacture as the basefitting 12 of the embodiment shown in FIGS. 2-3. In this embodiment,however, the base fitting is connected to a plurality of custom fittings130, 140 that are provided in a kit. In a preferred embodiment, the kitincludes multiple custom fittings from which the user can select toconfigure a custom assembly.

Similar to the custom fitting 30 described above, each custom fitting130, 140 is made from a SMA and has an input port that connects by aninterference fit with a port on the base fitting 112. Referring to FIG.4, the two custom fittings 130, 140 comprise a long and short coupling,respectfully, having a dry film lubricant 132 applied to the innerdiameter of at least one end of the coupling. The couplings areconnected to the base fitting 112 and tubing lengths 160 using the samecooling/deforming/heating method described above with respect to thecustom fitting 30 of FIGS. 2-3. The SMA couplings swage and coin theoverlapping outer surfaces of the base fitting 112 and tubing sections160 in the same manner as described with respect to the embodiment ofFIGS. 2-3.

In this embodiment of the assembly 110, the input leg 112 b of the basefitting 112 is connected to another fitting assembly, which in thisembodiment comprises the same assembly 10 described in FIGS. 2-3. Inthis embodiment, the base 112 and base 12 are made from the samematerial and are connected using prior art techniques such as swaging,welding, etc.

A hybrid fluid-flow fitting assembly in accordance with anotherpreferred embodiment is illustrated in FIG. 5 and is designated byreference numeral 210. The assembly 210 generally comprises a basefitting 212 and a plurality of custom fittings 230, 240, which areconnected at one end to the output legs 212 c, 212 d, respectively, ofthe base fitting 212, and at the other end to additional fittings 262,which in this preferred embodiment, comprise beam seal adapters. Thebase fitting 212 is identical in structure and manufacture as the basefitting 12 of the embodiment shown in FIGS. 2-3. In this embodiment,however, the base fitting 12 is connected to a plurality of customfittings 230, 240 that are provided in a kit. In a preferred embodiment,the kit includes multiple custom fittings from which the user can selectto configure a custom assembly.

Similar to the custom fitting 30 described above, each custom fitting230, 240 is made from a SMA and has an input port that connects by aninterference fit with a port on the base fitting 212 and a port on theadaptors 262. Referring to FIG. 5, each of the two custom fittings 230,240 comprises a coupling having a dry film lubricant 232 applied to theinner diameter of at least one end of the coupling. The couplings areconnected to the base fitting 212 and the adapters 262 using the samecooling/deforming/heating method described above with respect to thecustom fitting 30 of FIGS. 2-3. The SMA couplings swage and coin theoverlapping outer surfaces of the base fitting 212 and adapters 260 inthe same manner as described with respect to the embodiment of FIGS.2-3.

The inventive assemblies, kit and assembly methods described aboveprovide significant advantages over and solve several shortcomings ofthe prior. The invention provides a quick, inexpensive and secureconnection between fittings made of different materials and made bydifferent manufacturing methods. Since the base fittings are preferablyformed by ALBF, the base fitting can have a unique and/or complex shapeand be made from minimal material, which reduces overall weight comparedto fittings machined from forgings.

ALBF fittings also typically have a smoother surface compared tofittings machined from forgings. Therefore, the inventive assemblieshave a smoother flow path compared to prior art fitting assemblies.

The compressive connection method of swaging and coining provided by theSMA fitting allows the base fitting to be connected to a variety offittings having disparate material composition, disparate construction,and/or a disparate production method. For example, the novel fittingassembly may include both lightweight, thin-walled components andthick-walled components.

Thin-walled fittings made by ALBF often have legs that are out-of-round,have surface imperfections, are short, and/or have non-uniform wallthicknesses. These limitations make ALBF fittings difficult orimpossible to weld or connect to swage fittings. The connection methodof the invention easily and reliably connects a thin-walled ALBF fittingto another custom fitting without welding or using prior art swagefittings.

It is to be understood that the description, specific examples and data,while indicating exemplary embodiments, are given by way of illustrationand are not intended to limit the present invention. Various changes andmodifications within the present invention will become apparent to theskilled artisan from the discussion, disclosure and data containedherein, and thus are considered part of the invention.

1. A hybrid fluid-flow assembly, comprising: a) a base, fluid-flowfitting that has been formed by axial load bulge forming from a sheet ofmetal, having an input port, at least one output port, and a fluid-flowchannel connecting said input and output ports; b) a custom, fluid-flowfitting that has been machined from a shaped-memory alloy, having aparent shape, a martensitic shape, an output port, an input port havingan inner diameter in its martensitic shape slightly larger than theouter diameter of the output port of the base fitting, and a fluid-flowchannel connecting said input and output ports; wherein said input portof said custom fitting is connected to the output port of the basefitting by an interference fit.
 2. The assembly recited in claim 1,wherein said custom fitting has been machined from a cast, shaped-memoryalloy.
 3. The assembly recited in claim 1, wherein said input port ofsaid custom fitting is connected in its parent condition to the outputport of the base fitting.
 4. The assembly recited in claim 1, whereinsaid custom fitting and base fitting are made from dissimilar materials.5. The assembly recited in claim 1, wherein at least one output port ofthe base fitting was out-of-round prior to forming the interference fit.6. The assembly recited in claim 1, wherein the wall thickness of theoutput port of the base fitting are non-uniform.
 7. The assembly recitedin claim 1, wherein the base fitting and custom fitting are made frommaterials that are not weldable together.
 8. A fluid-flow assembly kit,comprising: a) a base fluid flow fitting that has been formed by axialload bulge forming from a sheet of metal, having an input port, at leastone output port, and a fluid flow channel connecting said input andoutput ports; b) a plurality of custom fluid-flow fittings that havebeen machined from a shape memory alloy, having a parent shape, amartensitic shape, an output port, an input port having an innerdiameter in its deformed condition slightly larger than said output portof the base fitting, and a fluid flow channel connecting said input andoutput ports; wherein said input port of said custom fitting isconnected to the output port of the base fitting by an interference fit.9. The kit recited in claim 8, wherein a plurality of said customfittings have a different output port.
 10. The kit recited in claim 8,wherein said plurality of custom fittings have been cooled to anddeformed at a temperature below their transition temperature.
 11. Thekit recited in claim 10, including means for storing the custom fittingsbelow their transition temperature.
 12. A method of making a customfluid flow assembly, comprising the steps of: a) forming a base fluidflow fitting from a sheet of metal, said base fitting having an inputport, at least one output port, and a fluid flow channel connecting saidinput and output ports; b) machining a custom fluid-flow fitting from acast shaped-memory alloy, said custom fitting having a parent condition,a martensitic condition, an input port having an inner diameter largerslightly larger than at least one output port of the base fitting in themartensitic condition, at least one output port, and a fluid flowchannel connecting said input and output ports; c) creating a mechanicalconnection between the base fitting and the custom fitting by installingthe input port of the custom fitting over an output port of the basefitting.
 13. The method recited in claim 12, including the step offorming a leak free seal between the custom fitting and base fitting byheating the custom fitting until the base fitting returns to its parentcondition.
 14. The method recited in claim 12, including the step ofproviding a plurality of custom fittings having different output ports.15. The method recited in claim 12, including the step of reducing theweight of the assembly by axial load bulge forming the base fitting froma sheet of metal.
 16. The method recited in claim 12, wherein themechanical connection is created by deforming the custom fitting,installing the custom fitting on the output port of the base fitting,and heating the custom fitting to form an interference fit between theports.
 17. The method recited in claim 12, wherein the mechanicalconnection is created by deforming the custom fitting at a temperaturefar below room temperature, installing the custom fitting on the outputport of the base fitting, and allowing the custom fitting to warm toroom temperature.
 18. The method recited in claim 12, wherein themechanical connection is created by deforming at least the input port ofthe custom fitting at a temperature far below its transitiontemperature, installing the custom fitting on the output port of thebase fitting, and allowing the custom fitting to warm to roomtemperature.
 19. The method recited in claim 18, wherein the input portof the custom fitting is deformed to an inner diameter larger than theouter diameter of the base fitting.
 20. The method recited in claim 12,wherein the mechanical connection is created without welding orcrimping.